Hi Gang,
We're approaching the final moments of our planning stages. We're doing a (primarily) DIY 18x36 IG, and a 20x30 auxiliary building. I'm outsourcing the footings/block foundation of the building. The guy who I am currently looking at signing the deal with for the foundation also claims to do a lot of pool work for the local pool companies. He says that they typically pour a base layer of ready mix 20 mpa concrete at 2 inches thick, and then the next day do a 1 inch skim/smooth coat using type "s" masons mortar. He claims that this is a more cost effective solution over vermiculite/portland.

Thoughts from the peanut gallery?

I was under the impression that the vermiculite solution was better for a couple of reasons: 1) the vermiculite "cushions" the vinyl and reduces frictions/wear, and 2) is water permeable preventing/reducing ground water forces from lifting the base, 3) possibly being a better insulator.

Anyway, I am interested in this if it is more cost effective, as there is a reason we're doing the DIY solution. But I don't want to risk future issues, and would rather do it once and be confident that it's done with value/dollar in mind.

Thanks for your thoughts! - John

IMO do pool krete only.